Removal of nickel and vanadium from residual stocks



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United States Patent REMOVAL OF NICKEL AND VANADIUM FROM RESIDUAL STOCKSLuke W. Corbett, Westfield, N.J., assignor to Esso Research andEngineering Company, a corporation of Delaware Filed Apr. 3, 1959, Ser.No. 803,931

10 Claims. (Cl. 208-251) The present invention relates to the removal ofmetallic contaminants from petroleum oil and more particularly relatesto an improved process for the removal of nickel andvanadium componentsfrom high boiling petroleum gas oils and residua.

It has long been recognized that petroleum gas oils and residua thatinclude constituents boiling in excess of about 950 F. normally containiron, nickel, vanadium and other metallic contaminants which have anadverse eifect upon various catalysts employed in petroleum processingoperations and upon combustion equipment wherein such petroleumfractions are burned as fuel oils. In operations such as catalyticcracking, hydrofining and the like, the presence of very smallconcentrations of these contaminants in the feed stream leads to rapidpoisoning of the catalysts causing a significant decrease in the productyield, an increase in coke and gas production, and a marked shorteningin the life of the catalyst. In residual type fuels, such contaminantsattack the refractories used to line boilers and combustion chambers;cause slagging and build-up of deposits upon boiler tops, combustionchamber walls and the blades of gas turbines; and severely corrode hightemperature metallic surfaces with which they come into contact.

The advent of high-speed gas turbines has required the removal ofsubstantially all of the metals content from fuels. Even as little as 2p.p.m. of vanadium is injurious to these turbines and requires theaddition of an additive such as magnesium oxide. These additives, whilethey lessen the corrosion caused by the metals, create an undesirableash which erodes the high-speed turbine blades.

Although there have been numerous methods proposed in the past forremoving these contaminants from high boiling petroleum fractions, ithas been found that such methods are largely ineffective in removingsubstantially all of the metals. As a result, it has generally beennecessary to restrict high-speed gas turbine fuels to those fractionswhich do not contain the contaminants in high concentration.

It has been found in accordance with the instant invention that suchmetallic contaminants may be removed by subjecting the contaminated oilto oxidation, preferably by air-blowing, and thereafter deasphalteningthe oxidized oil. The term deasphaltening has been coined for thepurpose of this invention. It will be defined subsequently.

The drawing further illustrates the invention by means of a schematicdiagram. Residual stock taken from tank 1 is passed through line 2 andpreheated in furnace 3. This preheated oil passes through line 4 intooxidizing drum 5. Air, after it passes through knock-out drum 6, passesthrough line 7 into the oxidizing drum and is sprayed through air spray8 into the residual oil. Since the process is exothermic, it isdesirable to partially enclose the oxidizing drum 5 in a veritableinsulating shield 9 which may be cooled by an external pump circuit.

This removal of heat from the system allows the use of higher air ratesthrough the residual oil. Quench steam or a small amount of waterintroduced through line 10 further serves to control the temperature.Air-blowing is preferably carried out in the temperature range of425-550 F. with typical air rates of 25-200 cu. ft. of air/min./ton ofbase being blown. The quantity of air which is used is another way ofcontrolling the exothermic reactions of the process, since the heat ofreaction is about 2 B.t.u./1b./asphalt/ F. softening point rise. Theair-blowing reaction involves dehydrogenation and polymerization leadingto the evolution of steam and small quantities of carbon dioxide. Thesegases are removed from the oxidizing drum 5 through line 11 and aredisposed of after they are condensed in barometric condenset 12. Theoxidized asphalt is removed through line 13 and passed to deasphalteningtower 14. This tower may range from a simple (l-stage) mixer settler toa complex (multi-stage) counter-current tower. A solvent, preferablypentane through octane, is introduced into the bottom of thedeasphaltening tower 14 from solvent accumulator 15 through line 16. Theasphaltenes leave the deasphaltening tower 14 through line 17, areheated in furnace 18 and passed through line 19 into stripper 20 whereinsmall amounts of solvent are removed through line 21 and recycled to thesolvent accumulator 15. The asphaltenes are removed from the stripper 20through line 22. The mixture of petrolenes and solvent leaves the top ofthe deasphaltening tower 14 through line 23 and is heated in heatexchanger 24 to flash off the solvent in stripper 25. The flashedsolvent leaves the stripper 25 through line 26 and is recycled to thesolvent accumulator 15. The product is removed from the bottom of thestripper 25 through line 27 and again heated, this time in furnace 28,and further stripped by passing through line 29 into stripper 30. Anyremaining solvent is recycled through line 31 to the solvent accumulator15. The final product is withdrawn from the bottom of the stripper 30through line 32.

The majority of the metallic contaminants in residual oils are found inthe asphaltenes. However, the petrolenes contain a sufficiently highconcentration of metals to create many of the difliculties referred toin the introductory paragraphs. It has been found in accordance with theinvention that these metallic contaminants are largely concentrated in aparticular fraction of the petrolenes. It has further been discoveredthat oxidation, preferably by air blowing, converts these metalcontaining petrolene fractions into asphaltenes. The subsequent removalby the deasphaltening process shown herein of the original asphaltenesalong with the petrolene fraction converted to asphaltenes effectivelyremoves substantially all of the metal contaminants.

The distinction between deasphaltening and conventional deasphaltingmust be maintained. Firstly, petrolenes and asphaltenes should bedefined. That portion of an asphalt that is soluble in a certain classof petroleum solvents is termed petrolenes, whereas those constituentsremaining insoluble are referred to as asphaltenes. See Abraham, Asphaltand Allied Substances, D. Van Nostrand Co., New York (1945) pp. 71 and1165. Deasphaltening is the process whereby petrolenes and as phaltenesare separated from a hydrocarbon mixture by means of these petroleumsolvents. The petroleum solvents are composed entirely of open-chainhydrocarbons with a gravity of 86-88 Baum, and at least of the solventdistills between and F. Pure solvents such as n-pentane, n-hexane,n-heptane or isooctane accomplish essentially the same separation andhave the advantage of uniformity of solvent composition. The data shownin Table II illustrate the physical and compositional difference betweenthese two basic components of asphalt. The differences in the twoprocesses can best be illustrated by comparing the yields and thecharacteristics of the products of the two processes when applied to aparticular residual stock.

As an example, two samples of Lagunillas pipe still residual having aspecific gravity of 1.011 were deasphalted and deasphaltened. In thedeasphalter 7 to 1 parts of propane were used in an eight-stage extrac-In the deasphaltening operation, normal hexane in a 10 to 1 ratio wasused in a one-stage extraction at 77 F. The following products wereobtained:

TABLE II Petrolenes Asphaltenes Weight Percent 85 15 Specific Gravity 60F. .973 1. 23 O/H Ratio by weight..... 7. 7 11.0 Softening Point, F.400+ Penetration 77 F Compo ition:

Percent Parai'fins and Naphthenes. 17 0 Percent Aromatic Oils 83 0Percent Asphaltenes 0 100 As can be readily seen from the character ofthe extracted oils, i.e. deasphaited oil in the first example, and thepetrolenes in the second, the two processes are quite different. Acomparison of the rejected material, i.e. precipitated asphalt andasphaltenes, further illustrates this diiference. Consider, for example,the specific gravity and the C/H ratio of the respective compounds. Thisdistinction is emphasized by measured composition analysis of theproduct fractions in which it will be noted that there is considerabledissimilarity in the respective fractions.

The practice of air-blowing asphalt stocks, fluxes and residuals is wellknown in the art. The resulting oxidized asphalt is harder, has bettertemperature susceptibility and weathering properties than the untreatedasphalt. The unox-idized asphalts have softening points in the range offrom about 70 to about 175 F. Although conversion of metal containingfractions begins with the start of air-blowing, it is desirable to haveat least a F. softening point rise in the material being treated. A risein softening point 100 F. or more, however, is preferred, while a risein softening point of 200 F. or more is considered impractical for thisinvention because of product handling problems. Furthermore, it has beenfound that essential conversion of metal containing compounds isaccomplished before this amount of softening point rise is reached.

Many modifications of air blowing are recited in patent literature. Anearly patent to Salathe, US. Patent No. 564,341, discloses the use ofair as an oxidizing agent. Davis, U.S. Patent No. 671,078, teaches theuse of potassium chromate, and Mittash et a1. U.S. Patent No. 1,487,020uses oxygen carrying gases for oxidation. In addition to these basicoxidizers many modifiers and catalysts have been discovered which alterthe physical properties of the resulting product or speed up theconversion time. The use of such modifiers and catalysts in the airblowing reaction is, of course, within the scope of this invention. Someof the agents which may be used are more fully described in thefollowing patents: Abson, US. Patent No. 1,782,186, chlorides of zinc,copper, iron; Hampton, US. Patent No. 2,115,306, aluminum chloride,sulfuric acid; Bradley, US. Patent No. 2,347,626, maleic anhydride;Hoiberg, US. Patent No. 2,450,756, phosphorus oxides, sulfides,chlorides; Van der Berge, US. Patent No. 2,465,960, nitrated phenols;Smith, US. Patent No. 2,506,283, calcium and magnesium oxides; Illman,U.S. Patent No. 2,640,803, fluorinated phosphoric acids, and Hardman,US. Patent No. 2,776,932, fiuobo'rate of metal above atomic No. 22.British Patent 518,655 shows the use of iron, copper, lead, manganeseresinates; British Patent 534,798 uses naphthenates, of cobalt,manganese, iron, lead, vanadium, zirconium, copper, etc.', and GermanPatent 208,378 shows manganese.

The above list of catalysts and modifiers are merely representative ofthose known in the art and are not intended to include all those whichmay be used in the practice of the invention.

If additives or chemical modifiers are employed the preferred materialswould be taken from the following: ferric chloride, phosphorouspentoxide, zinc chloride or maleic anhydride. The reason for this isthat their use for other purposes has been reduced to practice, andtheycan be handled in a practical and economical manner.

Solvents suitable for deasphaltening include n-pentane, n-hexane,n-heptane, iso-octane and 86-88" Baum petroleum naphtha or any mixturesof these. Other solvents of a similar type and boiling characteristicsmay be used. However, the above are readily available at a low cost andhave more satisfactory handling qualities.

The solvent to feed ratio may be varied from 3 to 25 depending upon theselectivity desired. The higher ratios accomplished greater selectivityof separation. However, for this invention the preferred ratio would beof the order of 8 to 10.

The advantages of the present invention are more clearly shown in thefollowing examples:

Example 1 Tia Juana Medium 550 vis. stock straight run flux with aninitial softening point of 94 F. was air blown to a 220 softening pointand then deasphaltened with n-hexane. The petrolene fraction obtainedwas analyzed for metals content and compared with the untreated flux.The following data were obtained:

TABLE III Wt. Vanadium Nickel Fraction Percent Fraction ppm. Percentppm. Percent Untreated Tia Juana Medium 450 100 31 100 Deasnhaltenedonly 87 184 35 24 75 Airblo'vn to 220 8.1. de-

asphaltened petrolenes.. 65 39 5 7 10 A Bachaquero residium with aninitial softening point of 100 F. was air-blown to a softening point of215 F. and deasphaltened with n-hexane. These data were The above twoexamples clearly show the value of air-blowing in accordance with theinvention. In the two examples treated, the metals content in thepetrolenes was reduced to less than of the total metals content of theuntreated flux. Failure to air-blow the stock results in unsatisfactorymetals removal; that is, well over 100 p.p.m. of metals remain in thepetrolenes. To attempt to treat the air-blown stock by conventionaldeasphalting would be highly undesirable. The air-blown stock is muchmore immobile than the oxidized material and has a softening pointgenerally in excess of 200 F. In order to solvent precipitate thisair-blown stock, unusually high solvent ratios and temperatures arerequired. At these high temperatures conventional deasphalting solvents,for example, propane, exert considerable pressures. In order to keep thesolvents in the liquid phase pressure throughout the deasphalter must bein excess of 400 p.s.i. The extremely low yield, i.e. less than ofdeasphalted oil is another drawback of deasphalting air-blown stock.Further, the 85% plus precipitated asphalt would be unwieldy because ofits excessively high softening point.

Many modifications of the above described examples can be made withoutdeparting from the scope and spirit of the invention.

What is claimed is:

1. An improved process for upgrading a metallic contaminated petroleumfraction including constituents boiling above 950 P. which comprisesoxidizing said fraction and thereafter solvent deasphaltening saidfraction.

2. The process of claim 1 wherein said oxidizing is accomplished byair-blowing.

3. The process of claim 1 wherein said solvent is a hydrocarboncontaining from five to eight carbon atoms, inclusive.

4. The process of claim 3 wherein said solvent is hexane.

5. An improved process for demetalizing a contaminated petroleumfraction, including constituents boiling above 950 F. and having asoftening point between and 115 R, which comprises air-blowing saidfraction thereby increasing said softening point from about 10 F. toabout 200 F.; thereafter contacting said fraction with a parafiinichydrocarbon solvent containing from 5 to 8 carbon atoms and thereafterwithdrawing a petrolene and an asphaltene fraction.

6. The process of claim 5 wherein from 3 to 25 parts of said hydrocarbonsolvent are added to each part of the petroleum fraction.

7. The process of claim 5 wherein from 8 to 10 parts of said hydrocarbonsolvent are added to each part of the petroleum fraction.

8. The process of claim 5 wherein the air-blowing is carried out at atemperature of from about 425 to about 550 F.

9. The process of claim 5 wherein the softening point rise is between100 and 200 F.

10. A process for extracting substantially metal-free petrolenes frommetal contaminated asphalts which comprises air-blowing said asphalt,extracting said petrolenes with a petroleum naphtha solvent having agravity of from about 86 to 88 Baum, at least of said solvent boilingbetween and F., and thereafter flashing ofi said solvent and recoveringpetrolenes essentially free of metals.

Short Oct. 8, 1940 Read July 23. 1957

5. AN IMPROVED PROCESS FOR DEMETALIZING A CONTAMINATED PETROLEUMFRACTION, INCLUDING CONSTITUENTS BOILING ABOVE 950*F. AND HAVING ASOFTENING POINT BETWEEN 70 AND 115*F., WHICH COMPRISES AIR-BLOWING SAIDFRACTION THEREBY INCREASING SAID SOFTENING POINT FROM ABOUT 10* F. TOABOUT 200*F., THEREAFTER CONTACTING SAID FRACTION WITH A PARAFFINICHYDROCARBON SOLVENT CONTAINING FROM 5 TO 8 CARBON ATOMS AND THEREAFTERWITHDRAWING A PETROLENE AND AN ASPHALTENE FRACTION.